Changes in the shape of joint bones are a possible cause of arthritic joint diseases. Bone anomalies can for example occur in the region of the hip joint which lead to bone collisions in the joint region when the leg moves and—in particular in the longer term—cause attrition complaints. In surgical correcting steps, the femoral head or acetabular rim—both are examples of joint elements in the terminology of the present invention—are for example returned back to their natural shape in order to prevent collisions between the femur and the acetabulum in the joint region, wherein the intention is to restore the natural shape of the femoral head.
In open (non-arthroscopic) surgeries, spherical templates are sometimes used in accordance with the prior art in order to check the sphericity of the femoral head. Using these and other currently used means, it is not possible to systematically compare the desired state with the current shape of the joint element accurately. In particular, it is not possible to monitor and control the abrasion depth to the necessary and desired level of accuracy.